Primary Care Corner with Geoffrey Modest MD: Flu Nasal Spray Ineffective

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By Dr. Geoffrey Modest

There was a recent CDC evaluation of the effectiveness of the live attenuated flu vaccine (LAIV), finding essentially no protective effect last year (see http://www.cdc.gov/media/releases/2016/s0622-laiv-flu.html ).

Results:

  • In May, the CDC found preliminary data of vaccine effectiveness for those 2-17 yo:
    • LAIV: 3% (CI: -49 to 37%), so no significant effect!!
    • Inactivated influenza vaccine (IIV): 63% (52-72) effective
  • Bottom line: “CDC’s Advisory Committee on Immunization Practices (ACIP) today voted that live attenuated influenza vaccine (LAIV), also known as the “nasal spray” flu vaccine, should not be used during the 2016-2017 flu season”
  • The annual flu vaccine for anyone >6 months old should be one of the shots: the inactivated influenza vaccine (IIV) or recombinant influenza vaccine (RIV)

Commentary:

  • There has been a pretty consistently poor showing for LAIV over the past few years: the prior 2 seasons found significantly decreased effectiveness as well. and before then, even when there was pretty much similar effectiveness of LAIV and IIV in kids, there were diminishing effectiveness in adults >30 yo (on my review of the age-based effectiveness published by the CDC)
  • These results were pretty surprising, since
    • LAIV is a live virus, and is associated with higher antibody responses, and some suggestion of more efficacy than IIV with influenza virus genetic drift
    • The flu virus attacks through the nasal mucosa, and the local IgA response to the live vaccine should increase its protection over the injected killed vaccine
    • Earlier studies found at least equal and some superior efficacy of LAIV: 80% in 2012
    • There was even early speculation that it could be given less often (perhaps every 2 years, given the increased immunogenicity)
    • As a result of the above logic, I have been preferentially using LAIV in kids, when appropriate, though not in those >30 yo
  • So, I am really not sure why there is less effectiveness for the live vaccine over the past several years. But the data speak volumes, given their consistency…. and we should not use this vaccine on anyone in the upcoming year or in the future, barring documented improvements in technology/efficacy.
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